The present invention is directed to the stabilization of crude acetonitrile, in particular, crude acetonitrile produced as a coproduct during the manufacture of acrylonitrile. In another aspect of the present invention, the stabilized crude acetonitrile obtained by the process described below is upgraded by catalytic treatment in a fluid bed reactor to produce hydrogen cyanide.
The manufacture of acrylonitrile by the direct reaction of propylene, ammonia and air over a catalyst in a fluid bed reactor is recognized worldwide and referred to as the "Sohio Acrylonitrile Process". In addition to the manufacture of acrylonitrile, the Sohio Acrylonitrile Process produces coproducts such as acetonitrile and hydrogen cyanide. Acetonitrile is a known commercial solvent. Hydrogen cyanide is an important substance which is frequently employed as a starting material for various organic reactions. Any improvements in the yields of these coproducts or upgrading of these coproducts would enhance the economic value of the Sohio Acrylonitrile Process.
Various patents disclose processes for the manufacture of hydrogen cyanide by reacting acetonitrile over ammoxidation or oxidation catalyst. For example, U.S. Pat. No. 3,516,789 discloses a process for the manufacture of hydrogen cyanide by reacting acetonitrile over an ammoxidation catalyst. This patent discloses that the feed of acetonitrile is purified to remove all impurities such as acrylonitrile and hydrogen cyanide. Japan Patent Kokai 73 81816 (CA80:108016a) discloses purification of acetonitrile by adding alkali, heating, treating with formaldehyde and distilling to remove HCN, acrylonitrile, etc. U.S. Pat. No. 3,911,089 discloses the preparation of hydrogen cyanide by the addition of methanol to the ammoxidation reactor used during the production of acrylonitrile. The addition of the methanol increases the yield of hydrogen cyanide. German Patent 1,146,861 discloses hydrogen cyanide production by the reaction of acetonitrile with molecular oxygen over an ammoxidation catalyst. Belgium Patent 623,100 also discloses the reaction of acetonitrile over an ammoxidation catalyst to produce hydrogen cyanide.
It has been observed that the direct vaporization of crude acetonitrile results in substantial plugging or fouling of the apparatus making the commercial practice of the process quite difficult. In U.S. Pat. No. 4,981,670 assigned to the assignees of the present application, crude acetonitrile is used as a source for the direct formation of hydrogen cyanide. A polymerization inhibiting agent is added to eliminate plugging and fouling observed previously during the use of crude acetonitrile for oxidation to HCN. It would be desirable to be able to utilize crude acetonitrile, especially crude acetonitrile coproduct from the Sohio Acrylonitrile Process, as a source for the manufacture of hydrogen cyanide by oxidation or ammoxidation without resorting to the complete purification of the acetonitrile as disclosed in U.S. Pat. No. 3,516,789 or the addition of a polymerization inhibiting agent as set forth in U.S. Pat. No. 4,981,670. The present invention is directed to providing a modified crude acetonitrile source ("stabilized crude acetonitrile") as the source for the manufacture of hydrogen cyanide.